Determination of Hammett Equation Rho Constant for the Hydrolysis of p-Nitrophenyl Benzoate Esters.

• Autores: Sheue L. Keenan, Karl P. Peterson, Kelly Peterson, Kyle Jacobson
• Localización: Journal of chemical education, ISSN 0021-9584, Vol. 85, Nº 4, 2008, págs. 558-560
• Idioma: inglés
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• Resumen

  • Seven p-nitrophenyl benzoate esters (p-nitrophenyl benzoate, p-nitrophenyl m-anisate, p-nitrophenyl p-anisate, p-nitrophenyl m-chlorobenzoate, p-nitrophenyl p-chlorobenzoate, p-nitrophenyl m-toluate, p-nitrophenyl p-toluate) were synthesized and characterized by students in a second-semester organic laboratory course. In a subsequent laboratory period, the rate constants for the base hydrolysis of these esters were measured by monitoring the formation of the p-nitrophenoxide ion by UV-vis spectrophotometry. The Hammett equation rho (?) constant for this hydrolysis reaction was then determined. The two-experiment sequence was developed to demonstrate structure�reactivity relationships and pseudo-first-order reaction kinetics. The students gained experience in organic synthesis and characterization, performing kinetics studies by spectrophotometry, and carrying out data analysis using spreadsheet software.